Question

miko is blowing up balloons for her little sisters birthday party. one of the balloons slips out of her hand before she ties it off, and it shoots through the air until it is empty. which statement explains what causes the balloon to accelerate?
a. the air leaving through the balloons mouth pushes on the air surrounding the balloon, so the balloon experiences a net force.
b. all air surrounding the balloon pushes the balloon forward.
c. the mass of the air leaving the balloon is greater than the mass of the balloon, so the balloon moves forward.
d. when the balloon pushes on the leaving air, the leaving air pushes back on the balloon, so the balloon experiences a net force.

Explanation:

This is based on Newton's third law of motion. When the balloon expels air (action), the air exerts an equal and opposite reaction force on the balloon. This reaction force is what causes the balloon to accelerate. Option A is incorrect because it's the reaction force of the leaving air on the balloon (not just the air leaving pushing on surrounding air) that matters. Option B is wrong as not all surrounding air pushes the balloon forward. Option C is incorrect as it's the force (from the reaction, not just mass comparison) that causes acceleration.

Answer:

D. When the balloon pushes on the leaving air, the leaving air pushes back on the balloon, so the balloon experiences a net force.